Method and apparatus for producing filaments



M 24, 1966 E. T. STRICKLAND ETAL 3,252,776

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METHOD AND APPARATUS FOR PRODUCING FILAMENTS Filed July '7, 1961 6 Sheets-Sheet 6 United States Patent 3,252,776 1 METHOD AND APPARATUS FOR PRODUCING FHLAMENTS Edward T. Strickland and Homer C. Amos, Palm Springs, Califl, assignors, by mesne assignments, to Brunswick Industries Research, Inc., Chicago, 11]., a corporation of Illinois Filed July 7, 1961, Ser. No. 122,543 8 Claims. (Cl. 65-8) The present invention relates to filaments, small spheres, commonly known as shot, and tear-shaped masses having extended tails.

In the past, filaments have been manufactured from organic substances and from inorganic substances which are known as glass-formers. Some of the better known glass-formers are silica, arsonic oxide, germanium oxide, lead oxide, sulphur and boron oxide.

Many organic substances and the inorganic glassformers have the common property that when they are cooled below their melting point, they will solidify in a non-crystalline state. These two classes of substances have another useful common property in that they have a melting point below 2000" C. Therefore, at the present time, there are a number of methods which involve heating one of these substances above its melting point, feeding it to a device which will separate it into liquid strands and then using another device to attenuate the strands into filaments of a desired diameter. At the present time, the two most common types of feed devices to form a liquid substance into strands are; containers that have a number of apertures in their bottom portion through which a substance feeds by gravity into the strands, and spinning devices, which have holes or grooves through which the liquid substance is separated into strands by centrifugal force. There are at the present time two widely used methods for attenuating such strands into filaments. One is mechanically pulling the strands and the other is directing a gaseous blast onto the strands. If the viscous forces in one of these substances were large, it has been necessary to add low viscosity materials to the substance in sufficient proportions to control the viscosity. Another method that has been utilized to control viscosity is varying the temperature of the liquid substance.

Silicon dioxide is an example of such a highly viscous substance. Other substances such as alumina cannot be manufactured by such methods of attenuating strands into filaments because their viscosity is low and their surface tension is high. With low viscosity to resist the high surface tension, any liquid strands or filaments that might be formed are quickly broken into short sections which form a multiplicity of spheres.

In the present terminology a glass-former is an inorganic substance which can be cooled to a rigid condition without crystallizing. Filaments of substantial length have not been manufactured from the inorganic su stances which are known presently as the non-glass-formers. These are those inorganic substances which are thought to assume crystalline structure very rapidly when solidifying. It has been possible to grow short filaments or whiskers of a few of the non-glass-former substances, but such growing processes are not adaptable to substantially continuous filaments. Nature has produced asbestos which is composed of short filaments of non-glass-former substances. Here again it is not possible to obtain substantially continuous filaments. The present invention seeks not only to provide a better method and apparatus for manufacturing inorganic and organic glass-former filaments, but it also makes it possible to manufacture filaments of substances from which filaments could not be produced from a melt previously. Therefore, the present invention encompasses new articles of manufacture 3,252,775 Patented May 24, 1966 which are substantially continuous filaments of the inorganic non-glass-former substances.

The present invention also makes it possible to make presently known non-glass-former' substances into a glass or non-crystalline structure by extremely rapid freezing. Such materials are particularly desirable for use in places where metal fatigue is a problem. The present invention, besides making it possible to freeze any meltable'substance in a non-crystalline state, also makes it possible to melt substances that have extremely high melting points and then to freeze them into a non-crystalline state. At least two new types of products not heretofore known are made possible by the present invention. The present invention produces filaments that can be made into wool and rovings which will withstand temperatures well above 3000 C.

Thus, it is an object of the present invention to provide substantially continuous filaments having a melting point above 2000 C. and to provide products composed of such filaments.

Another object of the present invention is to provide filaments of substances having a melting point above 3000 C. and to provide products composed of such filaments.

A further object of the present invention is to provide a method and apparatus for manufacturing filaments composed of substances having a melting point higher than 3000 C.

An additional object of the present invention is to provide a new and improved apparatus and method for the manufacture of both organic and inorganic filaments.

A still further object of the present invention is to provide an electric arc heating device in a high speed rotor for melting substances having a high melting point.

A still further object of the present invention is to provide a means for insulating and cooling the wall of the rotor to prevent the heat from the are or heated material from destroying the rotor.

A primary object of the present invention is to provide means for imparting high centrifugal force and kinetic energy to a substance in order to have it pour over an annular lip in a sheet which will form into liquid filaments under the influence of surface tension.

A further object of the present invention is to use this high centrifugal force and kinetic energy imparted to a substance by the high speed rotor to eliminate bubbles and impurities from the molten material in the rotor.

Yet another object of the present invention is to provide a method and apparatus for rapidly cooling the liquid filaments in the aforementioned object so rapidly that even non-glass-former substances will be solidified in a non-crystalline state.

A still further object of the present invention is to provide a method of manufacturing elements from substances having a high viscosity without the need for either adding substances of lower viscosity or for applying additional heat to raise the temperature appreciably above the melting point.

Yet another object is to produce filaments by use of a spinning rotor which is free of all mechanical devices such as apertures and grooves for separating a liquid substance into strands.

Yet another object is to impart sufiicient centrifugal force and kinetic energy to a liquid substance that it will pourover a lip in the form of a continuous sheet, that surface tension will then form the sheet into filaments and that the kinetic energy imparted to the molecule in these filaments will attenuate them to a desired diameter.

A still further object of the present invention is to produce filaments from non-glass-former inorganic substances which are round rather than prismatical in cross section.

Yet another object of the present invention is to solidify liquid filaments of a substance before surface tension can distort the filamentary shape of such liquid filaments.

A still further object of the present invention is to provide cooling methods for liquid filaments previously mentioned that can be adjusted to form filaments by freezing them before surface tension can destroy their filamentary shape, can allow the surface tension to break the filaments and draw each section into a small sphere and then freeze the liquid in such sphere shapes, or can allow surface tension to break the liquid filaments into tear-shaped masses with extended tails and freeze the liquid in this form before surface tension can draw the tails into spheres.

Further objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a front elevational view of an embodiment of the present invention;

FIGURE 2 is a sectional view of the embodiment shown in FIGURE 1 taken along the line 2-2;

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 2;

FIGURE 4 is a partial sectional view of the embodiment shown in FIGURES 1 and 3 taken along the line 4-4;

FIGURE 5 is a sectional view taken along the lines 5-5 of FIGURE 4;

FIGURE 6 is a sectional view taken along the lines 6-6 of FIGURE 4;

FIGURE 7 is an enlarged front elevational view of the centrifugal rotor shown in FIGURE 1 taken along the line 77 of FIGURE 8;

FIGURE 8 is an enlarged partial sectional and partial elevational view of the rotor shown in FIGURE 1;

FIGURE 9 is an elevational view of a modified embodiment of the present invention;

FIGURE 10 is an elevational view of a portion of the embodiment shown in FIGURE 9 taken along the line 10-10; and

FIGURE 11 is an enlarged sectional view of a central portion of the embodiment shown in FIGURE 9 taken along its center line.

While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplifieation of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. The scope of the invention will be pointed out in the appended claims.

Referring to FIGURES 1 through 4 first, an embodiment of the invention which includes a high velocity rotor is shown mounted on a suitable support structure. Two posts 10 and 11 are rigidly mounted in a base 12. A cover 13 is secured to the top ends of the posts 10 and 11. A stack indicated at 14 is connected to an aperture 15 in the top of cover 13 to remove gases collecting under the cover 13.

A diamond-shaped frame 16 consisting of two parallel members secured to each other by cross members is secured to the post 10 by a bracket 17 and to post 11 by a bracket 18. The frame 16 has an octagon-shaped portion 19, a square-shaped portion 20, and a set of cross members 21, securing the portion 20 to the portion 19.

A plate 22 is secured to the portion 20 to support an aluminum high speed rotor and means for supplying heat, a flow of particles, cooling water, and compressed gas for the operation of the rotor in accordance with the principles of the present invention. The rotor 30 is composed of a cylinder 31 which is a 2.75 inches in outer diameter having a set of turbine blades generally indicated at 32 rigid on its circumference, a front portion 33 and a rear portion 34. The front portion has a circular pour lip 35 surrounding a centrally located aperture, which is 1% inch in diameter. A water deflection flange 36 is rigid on the front portion 33 for the purpose of deflecting cooling water from reaching the general area surrounding the pour lip 35. The rear portion 34 has a cooling water deflection lip 37 surrounding the centrally located aperture. The front portion 33 and the rear portion 34 are constructed of four segments which are separated by an electrical insulating material. FIG- URES 7 and 8 show the segmentation of the front portion 33. An insulating material 38 is placed between the threads on cylinder 31 and the threads on front portion 33, and an insulating material 39 is placed between the threads on cylinder 31 and the threads on rear portion 34. Thus rotor 30 consists of nine electrically isolated parts.

Referring now to FIGURES 4 and 5, the rotor 30 is rotatably mounted by three sets of three bearings each. The bearings of .each set are spaced around the rotor at intervals of 120. Bearings 40, 41 and 42 comprise the first set of bearings. This set of bearings is mounted to maintain the radial position of the rotor by bearing against the cylindrical portion of the cylinder 31. The second and third sets of bearings maintain the rotor in a proper axial position. The axis of the rotation of the rotor is indicated at 43. A bearing 44 is one of the second set of bearings which prevents the rotor 30 from moving to the left, and a bearing 45 is one of the third set of bearings which prevents the rotor from moving too far to the right. All of these bearings are mounted in a member frame 46. The bearings 40, 41, 42, 44 and 45 are mounted in the apertures 47, 48, 49, and 51, respectively, which are threaded and provided with adjustment screws 52, 53, 54, and 56, respectively. The remaining bearings (not shown) are mounted in the frame member 46 in the same manner. The frame member. 46 is rigidly secured to the plate 22 for support.

Air under pressure for rotating the rotor is introduced into an air duct ring through an air duct 61. A series of three ducts 62, 63 and 64 are connected to the air duct ring 60 and to three nozzles 65, 66 and 67, respectively. These three nozzles direct a stream of air against the set of turbine blades 32 in order to rotate the rotor 30 at desired velocities between 30,000 and 120,000 revolutions per minute. The ring 60 is secured to the plate 22 and the nozzles are secured to the member 46.

In the present embodiment, the means of supplying heat to the rotor includes an electric canbon arc and means for controlling the position of the are. A pair of hydraulic cylinders 68 and 69 have a pair of hydraulic pistons 70 and 71, respectively, connected to a pair of push rods 72 and 73. The other ends of the push rods 72 and 73 are connected to cross members 74 and 75, respectively. The cylinders 68 and 69 are rigidly secured to the portion 20 of the frame 16 and the cross members 74 and 75 slidably mounted on fixed rods 76, 77, 78 and 79, which also are secured to the portion 20. The cross members 74 and 75 are constructed of an electrically non-conducting material. A A inch diameter carbon rod 80 and a /4 inch diameter carbon rod 81 are secured to the cross members 74 and 75, respectively, near one end of the rods. FIGURE 3 shows a means of supporting the other ends of the carbon rods 80 and 81. The rods pass through the apertures 82 and 83, respectively, in support blocks 84, and are held in position in these apertures by the cylindrical pressure shoes 85 and 86 which are mounted in the bores 87 and 88. Each bore contains a spring 89 and 90 under compression. The compression on each spring is adjusted by bolts 91 and 92, respectively, threaded into the bores 87 and 88, respectively. The blocks 84 are secured to the plate 22 by bolts 93 and 94. The rods 80 and 81 are insulated from one another by member 84' and are connected to an alternating current source 95 by leads 96 and 97. (Alternatively, the power source leads 96 and 97 may be connected to the bolts 91 and 92.) The source 95 provides an alternating current across the electrodes 80 and 81 to provide a high temperature electric,

are which creates suificient temperature to liquefy sub stances whose melting point is well above 3000 C.

The points of the carbon rods 80 and 81 are adjusted so that they are within the rotor 30 at approximately the same axial position. Their positions are maintained by the hydraulic pistons 70 and 71. A suitable control system is composed of a source of hydraulic pressure 98 connected to a set of two-way valves 99 and 100 by the hydraulic high pressure lines 101 and 102. The valve 99 is manually operated to selectively place hydraulic pressure on one side or the other side of the piston 70 by allowing high pressure fluid to flow into either a line 103 or a line 104. Low pressure fluid is returned from cylinder 68 through the line not receiving the high pressure fluid, valve 99, and a line 105 to the hydraulic source 98. The valve 100 is similarly operated selectively using lines 106 and 107 as high pressure lines and a line 108 as a low pressure return line. Thus the valve 99 is used to position the rod 80. This control system is manually operated to prevent the rods from burning down and moving an arc between them outside of the rotor 30. This control system also keeps the are operating over an extended volume as will presently be described.

A means for forming and transporting a flow of particles to the rotor area is shown in FIGURE 2, and a means for directing the flow into the rotor is shown in FIGURES 3, 4 and 6. A source of compressed gas such as a cornpressor 109 is connected to one end of a gas line 110 which has a pair of valves 111 and 112 and a filter 114 inserted therein. A container 115 is rigidly mounted and is filled with a substance either in granular or powder form from which filaments, spheres or tear-shaped masses are to be made. Particles of the substance feed from container 115 into a flow of gas from the source 109 through an aperture 116. The other end of the gas line 110 is secured in the blocks 84. The air pressure carrying the substance is sufliciently great to direct the particles of the substance past the electrodes against the layer of material 130 formed on the wall of the rotor 30, which layer acts as an insulating lining. The particles melt on this insulating material-on the rotating wall of the cylinder 31. When sufi'lcient particles have arrived, a sheet of molten mass resulting therefrom Will pour over the circular lip 35 under the influence of centrifugal force and kinetic energy provided by the spinning rotor 30.

Cooling water is introduced under pressure through the water lines 121, 122 and 123. 'The line 121 is connected to the water channel 124 in the frame member 46. A

series of water passages as indicated at 125 connect the circular water channel 124 to the outer surface of the cylinder 31 of the rotor 30. When water is applied under pressure through line 121, circular channel 124 and the set of water passages as indicated at 125, it is sprayed on the center portion of the cylinder 31 to thereby carry off a large portion of the heat being transmitted through molten substances and insulating material in the rotor to the cylinder 31. A circular water channel 126 is connected to the pipe 122. A set of water jets 127 connect to the annular water passage 126 and are utilized to spray water onto the outside of the water deflection lip 37 on the rear portion 34 of the rotor 30. The Water inlet 123 is connected to a circular water channel 128 which is in turn connected to a series of Water jets as indicated at 129, to spray cooling water on the outer diameter of the front deflection flange 36. Thus, cooling Water under pressure is sprayed on the cylinder 31 on the front lip and rear portions to carry away a large quantity of heat. This is of particular importance when the rotor contains substances having melting points above the melting point of the metal of the rotor 30. An additional method of keeping such a rotor sufliciently cool is by introducing a high temperature insulating substance into the rotor as indicated at 130 in FIGURE 4. Then the substance from which the filaments are to be made will be held by centrifugal force against the inner surface of the insulating material. Generally speaking, the insulating material should be in a solid state. However, for some applications, it is feasible to allow the insulating material to be in a molten state on its inside surface as are the substances from which filaments are to be made. The cooling water used to cool the rotor 30 is also utilized to provide a lubricant between the three sets of bearings and the rotor. As can be seen from FIGURE 4, the water will reach the bearings as its sprays off various parts of the rotor 30.

Referring to FIGURE 2, water is supplied under pressure from a source 131 by a water line 132, which is connected to the water lines 121, 122 and 123.

A water shield 133 and a shield spacer member 134 are provided to prevent a large quantity of water from being thrown into the filaments.

For the purpose of catching filaments, spheres or tearsh-aped masses after their formation, a shield 140 is provided around the rotor by securing it to the square-shaped portion 20.

Support for the hydraulic cylinders 68 and 69 is provided by a crosshead member 142 (FIGURE 2) which is rigid on members 141 and the rods 76, 77, 78 and 79. The other ends of said rods and members 141 are supported on the frame 19.

Referring to FIGURE 1, a compressor 145 provides high pressure air to the air duct 61 through an air line 146 which has a valve 147 and an air regulator 148 inserted therein.

Turning now to the operation of the embodiment of the present invention shown in FIGURES l to 5, let it be assumed that it is desired to make filaments from a nonglass-former inorganic material having a high melting point. An alternating current provided by the power source creates an electrical are between the ends of the carbon rods 80 and 81 to provide an extremely high temperature within the rotor. rods are kept properly positioned with the rotor by use of the hydraulic control system. The air streams directed against the turbine blades 32 rotate the rotor 30 at speeds of 30,000 to 120,000 revolutions per minute or higher. Powder or granular particles of the substance to be melted are directed by the air stream through passage and against the inner wall or insulating substance of the rotor 30. There the particles melt under the influence of the electric arc. Thus a molten mass of the substance is maintained as shown in FIGURE 1. As the rotor becomes filled, a portion of the molten mass will flow over the edge of the lip 35. The centrifugal force on the molten mass at the lip 35 is in excess of 250,000 gs at a rotational velocity of 120,000 revolutions per minute. Thus all air and other less dense impurities are forced inwardly from the molten mass of the substance by the centrifugation.

Any substances which are more dense are forced to the outside and cannot reach the por lip 35. When the rotor 30 is operating at any rotational velocity above 30,000 revolutions per minute a layer of a pure substance is created. Many substances of high viscosity such as silicon dioxide cannot be completely purged of gas or other impurities by the spinning rotors which have been used in the glass making art in the past because there was not sufiicient centrifugal force to overcome the high viscosity which trapped the impurities. The radius of the rotor and the rotational velocity determines the amount of centrifugal force and the amount of kinetic energy imparted to each molecule of the liquid substance being spun within the rotor.

The amount of kinetic energy imparted to each molecule of a substance varies as the square of the radius of the lip and as the square of rotational velocity. The amount of centrifugal force imparted to each molecule at the lip varies linearly with the radius and as the square of the rotational velocity. Therefore, increasing the rotational velocity changes kinetic energy and centrifugal force in a similar manner, while increasing the radius increases the kinetic energy much faster than the centrifugal force.

The ends of the carbon Therefore, other size rotors than the one described in the embodiment may be utilized. For example: a 1.0 inch diameter lip at 32,000 r.p.m. may be used to produce silicon dioxide with a centrifugal force of 14,500 gs or a 1.25 inch diameter lip at 53,000 r.p.m. may be used with a centrifugal force of 49,700 gs; mullite may be made into filaments with a 1.25 inch diameter lip and rotational velocities of 39,000 to 53,000 rpm; and zircon may be into filaments with a 1.0 inch diameter lip and rotational velocities of 38,000 to 53,000 rpm. Thus, combination of ranges of centrifugal force and kinetic energy may be found for each substance which will cause filaments to be formed in accordance with the principles of the present invention. Varying the rotational velocity varies both the centrifugal force and the kinetic energy in the same manner, while varying the lip radius varies each in a different manner so that the kinetic e e y may be varied in relationship to the centrifugal force.

When the level of the liquid substance in the rotor has exceeded the lip 35, it will commence to flow over the lip forming a thin sheet spreading out radially. At this point centrifugal force will be forcing the molecules right at the lip 35 to move out radially under the influence of centrifugal force and the kinetic energy previously imparted to them will tend to make them move tangentially from the lip. The kinetic energy imparted to the molecules while the molecules are in the rotor and the additional kinetic energy imparted to the molecules through centrifugal force produced by the cohesive forces between the molecules will cause the molecules to form an expanding sheet rather than break off'into tear-shaped masses which detach themselves from the main mass of liquid material. The kinetic energy thus imparted to the molecules causes the sheet to expand against the restraining viscosity forces and become thinner until the surface tension of the sheet breaks the sheet into a multiplicity of liquid filaments expanding outward in arcs from the lip 35. Once this action has started the kinetic energy imparted to the molecules which have gone ahead will tend to continue to pull each individual filament that has been started into a uniform diameter. Considering each filament being formed for the moment, the surface tension which breaks the sheet into such filaments will shortly thereafter tend to distort and if allowed to continue its effect, will break each filament into sections. Therefore, it is necessary that a cooling fluid be provided in the area just beyond that area in which it is required to maintain the filaments in a liquid state. In the embodiment of the invention shown in FIGURES 1 through 7, the coolant is atmospheric air. The filaments passing into the atmospheric air are very rapidly chilled so that they solidify before surface tension can distort their filamentary shape. The chilling of the substance has occurred within a microsecond of the time that the substance was formed into filaments. The chilling has been so rapid that the molecules have not had an opportunity to re-orient themselves into crystalline form. Therefore, they have been frozen into a solid in a non-crystalline or glass for-m, although the substance is not what is presently considered one of the glass-former substances. Therefore, the present invention has the capability of forming a glass of any meltable substance, even though it is inorganic and a nonglass-former.

It will be recognized by those skilled in the art that the relative effects of viscosity and surfacetension of a given substance must be considered in determining the size of rotor, the rotational velocity of the rotor, the temperature of the cooling fluid and the time required to freeze the liquid filaments after their formation. In utilizing the present invention to form filaments from a highly viscous substance such as silicon dioxide, it is necessary to have sufficiently high centrifugal force and kinetic energy imparted :to the liquid silicon dioxide to overcome its high viscosity. When a substance such as alumina is used, which has a very low viscosity, much less centrifugal force and kinetic energy are required.

However, the high surface tension of alumina makes it necessary to very quickly freeze the liquid filaments before they are distorted. At this point the low viscosity which is at first an advantage is now of little aid in slowing down the effort of surface tension to distort and break the filaments. Thus, the rotational velocity, the time between the formation of the liquid filaments and entry into a cooling fluid and the relative temperature of the cooling fluid are of prime importance. In the utilization of silicon dioxide, its high viscosity greatly resists the effort of the relatively low surface tension to distort and destroy the liquid filaments. Therefore, these considerations are of relatively less importance in the use of silicon dioxide.

If it is desired to have the alumina frozen in a noncrystalline state, even more rapid cooling is required than is required to overcome the damaging effects of its surface tension; Silicon dioxide, on the other hand, is one of the recognized glass-formers and therefore can cool relatively slowly without crystallizing. Thus, in utilizing the present invention to make filaments of a given substance, not only the viscosity and surface tension must be considered individually, butalso the interaction of viscosity and surface tension must be considered.

A high speed rotor such as described here has the tendency to pump air out along its open ends in a radial fashion. The air thus pumped out is replaced by air sucked in along the axis of the rotation of the rotor. The rotor and the part of the structure 126 which blocks the aperture at the rear of the rotor, and the direction of the air being introduced with the material by the passage 110 are all designed to produce a resultant flow of air from the tips of the electrodes and 81 outwardly through the front open aperture of the rotor. The adjustment of the proper flow of air may be aided by boring holes through a portion of the block 84 at the rear aperture of the rotor. When an are initially strikes over a minimum path between the electrodes 80 and 81, it produces an ionized area through which the ions tend to continue moving and carry current, but the movement of the gas carries the ions toward the front of the rotor and expands the path length. The gas continues to carry the ionized path outwardly in the form of a loop. This action continues until the ionized path assumes a shape which not only covers a good portion of the molten substance in the rotor, but also loops out over the pour lip 35. On each successive cycle of the expansion of the are, it will move from the direct path gradually outward until it assumes a path approximately as shown in FIGURE 4.- At this point the elongated path will have more resistance although ionized than a direct path between the electrodes. At this point the are along the extended path will be extinguished and a new are will strike along a direct path in the tips of the electrodes. The cycle of the arc striking at the tips and moving outward will continually repeat itself, keeping the substance in the rotor in a molten state and keeping the substance as it pour-s over the lip and separates into liquid filaments sufficiently hot that it does not freeze before surface tension has formed the filaments. However, it does not extend far enough to interfere with the sudden freezing by a cooler fluid, such as atmospheric air in the embodiment now being described, that the surface tension can distort the filamentary shape. The outward movement of the arc creates a noticeable amount of mixing of the gases that momentarily remain within the rotor. aids in the transfer of heat from the arc to the substance on the internal walls of the rotor.

As described previously, the cooling water is suflicient to prevent the rotor from 'being distorted or melting even though the heat being transferred'to the substance in the rotor is sufficient to not only melt the rotor but to melt the substance which has a much higher melting This mixing point. If this cooling effect is increased, it can be utilized to freeze the layer of the molten substance along the internal wall and thereby form a solidified covering lip over lip 35. Thus a solidified lip of the substance covers and protects the original lip 35. This is illustrated in the cross sectional view of the rotor in FIGURE 8. Whenever erosion or excessive temperature causes a piece of the lip thus formed to break off, the open area is immediately filled with a quantity of the liquid substance and the cooling effect then freezes that quantity of substance in the break, thus causing the lip to be self-healing.

It will be recognized by those well skilled in the art that the present invention is different from all previous processes involving centrifugal rotors in that a combination of greater heat for melting substances and a method of imparting a high kinetic energy to the molecules of the heated substance makes it possible to draw the filaments out into uniform constant diameters. Where previously a small chunk or drop would come off and would be followed by a droplet tail which would form the filament, it is no longer necessary. or desirable in the present invention to have a device for breaking up the molten material into filaments such as apertures or grooves. Thus the present invention has made it possible to produce new structural and insulating materials which were not heretofore known. An example is filaments of zircon which has -a melting point of 2550 C.

If the filaments thus spun off are gathered to form a wool, they will provide an insulating material which can be utilized for such purposes as high speed, high altitude and space vehicles or for insulation in equipment which is heated to extremely high temperatures.

The substance from which it is desired to make filaments may not require excessive heat or any additional heat at all. For example, there may be a requirement to produce filaments from water. In such a case, water or other substance having a low melting point would merely be introduced into the rotor without the necessity of the heating element. However, when the substance having a low melting point pours over the lip 35 and is formed by surface tension into liquid filaments, a much colder fluid must be available just beyond this point into which the liquid filaments would pass and be chilled below their freezing point. As will be described presently, the fluid into which the liquid filaments pass to be solidified may be a liquid as- Well as a gas. The speed at which they are traveling combined with their small diameter allows them to travel into a liquid as well as into a gas without being distorted before they are frozen in their filamentary form. Thus, the present invention is capable of producing inorganic non-glass-former filaments regardless of the melting point of the inorganic non-glass-former substance. When it is desired to make filaments from an organic or an inorganic glass-former substance, the present invention has the advantage over past products in that it produces filaments which are almost completely devoid of shot or chunks. Also, a large number of filaments can be produced by small economical apparatus without a continual manual repair of the filaments. Associated with this characteristic of self-repair in the filaments is the advantage that the filaments are much more uniform in total cross sectional area than is possible with previous methods of manufacture.

If the cooling fluid is removed sufficiently far from the rotor, surface tension will cause the liquid filaments to break and form into a series of small spheres before they are frozen into a solid. There are at the present time a number of applications for such small spheres which are commonly referred to as shot. If the cooling fluid is removed only far enough for the surface tension to break the liquid filaments into tear-shaped masses with elongated tails before being frozen, the resulting product will be of such shape. Thus, it may be seen that the present invention may be utilized to produce any type of product between a continuous uniform filament and spherical shot which may be desired. Although it appears at the present time that there is a greater de mand for continuous filaments in the commercial market, the other product just described may at times have equal importance.

Unlike artificially grown short filaments or the short asbestos filaments found in nature, the filaments which can be produced by this invention will be circular in cross section rather than prismatic regardless of whether the filaments have been frozen soon enough to retain the substance in a non-crystalline form. Even if they are not frozen soon enough to prevent them from crystallizing, the general circular shape will be retained unless the filaments are so thin that they are only a few crystals in diameter.

Referring now to FIGURES 9, 10 and 11, a more efficient embodiment is illustrated. Two rotors as illustrated in FIGURES 1 through 8 are placed with their pour lips in close proximity to each other. Elements illustrated in this second embodiment corresponding to elements in FIGURES 1 through 8 have similar numbers with the addition of a small subscript a or b. The primary difference between the embodiment of FIGURE 1 and the embodiment shown in FIGURE 9 is that the embodiment in FIGURE 9 has one electrode for each rotor. As illustrated in FIGURE 11, the ionized path for the discharge of the electric are between electrodes and 151 is down the center of the two rotors 30a and 30b. The radiant heat lost through the aperture formed by the lip 35 in FIGURE 4 is now greatly reduced by the fact that the tWo rotors are facing each other. Thus the heat that is radiated from the rotor 30a is directed primarily into the rotor 30b and vice versa. The efficiency of this modified embodiment shown in regard to heat losses is greatly improved. With the lips 35a and 35b in close proximity to each other, it is no longer necessary to have the discharge path of the electric arc flare out over the lips. Thus the flaring action as described for the embodiment illustrated in FIGURES 1 through 8 is no longer required. Both the lips 35a and 35b are sufiiciently hot that they do not cause cooling of the filaments until the filaments are properly attenuated to the desired diameter. The modified embodiment has a further advantage that the electrodes 150 and 151 can be positioned for the continuous operation of a long are. Such a long are can continuously require the power source to have a large voltage drop between the electrodes with the accompanying small current flow for a given amount of power dissipation. Since the heat produced by the arc is directly related to the electrical power expended in the arc, it is advantageous to have a high voltage and a low current in the electrical system for the lower the current in the supply system and the connecting leads, the lower will be the loss of electrical energy outside of the arc itself.

In order to support the two rotors in such close proximity to each other and to provide for the positioning of the rods 150 and 151, a system of structural support elements and a rod drive device are provided. Referring to FIGURE 9, a post is rigidly secured in a base (not shown). A support platform 153 having a set of upright members 156 rigid thereon is bolted on the top of post 152 by bolts 155. A bar 157 and a bar 158 are rigidly supported by the set of members 156. The plate 22a is secured to the bar 157 and the plate 22b is secured to the bar 158, and the plates 22a and 22b are secured to the remaining elements surrounding the rotor as described for the first embodiment, the elements except for the rods are supported and operate in. the same manner as those in the first embodiment.

A mechanical drive is utilized for the rods in the modified embodiment. A pair of drive support members 159 are secured to bar 157 to support a drive 160 for rod 150, and a pair of drive support members 161 are secured to bar 158 to support the drive for rod 151. Since the drives are similar, only the drive for rod 150 will be described in detail.

Referring now to FIGURE 10, a base 163 is rigid on the device support members 159. An electric motor 164 is secured to the base 163 and has an output drive shaft 165 which rotates a set of gears 166 to drive a shaft 167. The gears are arranged to produce an increased torque to shaft 167. The shaft 167 is rotatably supported in bearings 168 and 169 which are mounted in a housing 170. The housing 170 is rigidly secured to the base 163. Two wheels 171 and 172 are mounted on the shaft 167 to move the rod 150 axially whenever the shaft 168 is rotated by the motor 164. An idler wheel 173 is mounted on a shaft 174 which is rotatably mounted in the bearings 175 and 176. The bearings are secured in the housing 170 in positions which allow the wheel 173 to press the rod 150 against the wheels 171 and 172 for better traction.

An electronic power source 178 has a ground lead 179 connected to the motor 164 and two leads 180 and 181 connected to contaacts 182 and 183 of a switch 184. A movable contact 185 is connected to the motor 164 by a lead 186. The power source supplies positive voltage to the contact 182 and negative voltage to the contact 183. Thus, an operator may move the rod 150 axially in either direction by applying either positive or negative voltage to rotate the motor.

A method of positioning a cooling liquid rather than a cooling gas is illustrated in FIGURES 9 and 11. A container 190 is rotatably mounted about the axis 43a by a support 191. It is rotatably driven by a belt 192 connected to a motor 193 at a speed sulficient to impress at least 1-g of centrifugal force on any fluid with which it might be filled. Thus the filaments, small spheres, or small tear-shaped masses will pass into a liquid soon after they leave lips 35a and 35b.

It is of particular importance to note that in utilizing the apparatus and methods herein described, the resulting filaments are unlike filaments made by former processes in that they contain an extremely small proportion of chunks. Wherever a spinning rotor has been used in the process for making filaments from organic or glass-former substances, the proportion of chunks of the substance among the filaments has been relatively high. The present invention, unlike processes which draw filaments through apertures in a container, is capable of continuously producing filaments even though a filament will break occasionally. In the present invention a new filament automatically replaces the broken filament because the number of filaments coming off the rotor at any time will of necessity not vary by more than about one percent. However,, former processes, which utilized drawing filaments through apertures, required that a workman repair each filament each time a break would occur. Such devices were not self-repairing.

The present invention includes a' vast number of new filaments and products which may be manufactured from filaments. In the past organic and glass-former filaments have been used for many products from cloth to automobile bodies and hulls of vessels. The new articles of manufacture that the present invention adds to the filament field include continuous filaments composed of nonglass-former inorganic substances, fused filaments composed of non-glass-former substances, non-crystalline filaments composed of non-glass-former inorganic substances, continuous filaments composed of substances having melting points above 2000 C., filaments composed of substances having melting points above 3000 C., and filaments having a non-prismatic shape composed of a non-glass-former inorganic substance. The barriers of high viscosity, low viscosity with low surface tension, crystallization upon solidification, high temperature, and prismatic crystal growth which have prevented the manufacturing of such products in the past, have been overcome.

Any of the new filaments may be immediately gathered up from the shield in the form of wool for insulation, cushioning, and other uses, or the filaments may be retained in their filamentary form for use in cloth, structures, or other finished products.

In addition to filaments, new products such as shot or tear-shaped masses composed of the above listed classes of substance are within the scope of the present invention.

We claim:

1. The method of making filaments comprising: centrifuging particles of an inorganic non-glass-former, simultaneously heating the particles to a temperature in excess of 2000 C. to melt them into a liquid mass, and releasing the liquid mass from the centrifuging to allow it to form filaments.

2. The method of making filaments: centrifuging particles of an inorganic non-glass former, simultaneously heating the particles to a temperature in excess of 2000 C. to melt the particles into a liquid mass, releasing the liquid mass from the centrifuging to allow it to form liquid filaments, and solidifying the filaments in a fluid before surface tension can distort their filamentary shape.

3. The method of making filaments comprising centrifuging the molecules of a liquid substance in a rotor about an axis, said substance being a solid at sea level ambient temperatures, rotating an annular edge of said rotor in a plane perpendicular to said axis, said annular edge having been covered with a layer of said substance in a solid state, which heals itselffrom the liquid substance whenever a break occurs, cooling said edge to keep said layer in a solid state, and adjusting the angular velocity of the rotor to pour a continuous sheet of said substance in a liquid state over said edge of said rotor to allow surface tension in said sheet to continuously form said sheet into a multiplicity of liquid filaments and to allow the kinetic energy of the molecules of said substance to attenuate said liquid filaments to a desired diameter.

4. The combination of a hollow rotor having an internal wall, means for heating an inorganic non-glassformer substance to a temperature in excess of 2000 C. to rapidly liquefy said substance in said rotor, means for depositing said substance on the internal wall, means for rotating said rotor at high rotational velocities, and aperture means in said rotor for releasing a continuous sheet of said liquid substances from said rotor whereby a multiplicity of liquid filaments are formed by surface tension from said sheet.

5. The combination of a hollow rotor having an internal wall, means for rotating said rotor at high rotational velocities, means for conveying a flow of particles of a substance to said wall, a pair of electrodes having ends positioned in said rotor, a source of alternating current connected to said electrodes producing an electric are between said ends to melt said particles into a liquid mass of said substance, said liquid mass being pressed against said wall by centrifugal force, and means for releasing a continuous sheet of said liquid substance from said rotor whereby a multiplicity of liquid filaments are formed by surface tension from said sheet.

6. The combination of a hollow rotor having an internal wall, means for rotating said rotor at high rotational velocities, means for conveying a flow of particles of a substance to said wall, a pair of electrodes having ends positioned in said rotor, a source of alternating current connected to said electrodes producing an electric are between said ends to melt said particles into a liquid mass of said substance, said liquid mass being pressed against said wall by centrifugal force, means producing a movement of gases in said rotor away from the location of said ends of said electrodes to produce cyclic increases in the length of said are, and means for releasing a continuous sheet of said liquid substance from said rotor whereby a multiplicity of liquid filaments are formed by surface tension from said sheet.

7. The combination of a hollow rotor open at both ends and having an exterior portion and an internal Wall which terminates in a lip portion at each said end which extends radially outwardly from said rotor, means for rotating said rotor at high rotational velocities, means for conveying a flow of particles of a substance to said wall, heating means for melting said particles into a liquid mass of said substance, said liquid substance being pressed against said wall by centrifugal force and having a melting point higher than said rotor, flows of cooling fluid being directed against said external portion out to said radially extended lips to prevent deformation of said rotor, and mean-s for releasing a continuous flow of said liquid substance from said rotor, said lips extending radially for a distance sufiicient to prevent said cooling fluid from entering said rotor, from reaching said heating means and from interfering with the released flow of said liquid substance from said rotor.

8. In an apparatus for making filaments, the com bination of a hollow rotor having an internal wall, means for depositing a substance in a liquid state on said internal wall, means for raising the temperature of the substance above 2000 C. positioned within said rotor, means for rotating said rotor at high rotational velocities,

means for releasing a continuous sheet of said liquid substance from said rotor whereby a multiplicity of liquid filaments are formed by surface tension from said sheet, and a circular rotating container mounted to revolve around saidrotor releasing means with an open internal side to receive said liquid filaments, said container being filled with a cooling liquid and sufliciently closely surrounding said rotor to freeze said liquid filaments before surface tension can distort their filamentary form, said cooling liquid being held in said container by centrifugal force.

References Cited by the Examiner UNITED STATES PATENTS DONALL H. SYLVESTER, Primary Examiner.

MICHAEL V. BRINDISI, Examiner. 

3. THE METHOD OF MAKING FILAMENTS COMPRISING CENTRIFUGING THE MOLECULES OF A LIQUID SUBSTANCE IN A ROTOR ABOUT AN AXIS, SAID SUBSTANCE BEING A SOLID AT SEA LEVEL AMBIENT TEMPERATURES, ROTATING AN ANNULAR EDGE OF SAID ROTOR IN A PLANE PERPENDICULAR TO SAID AXIS, SAID ANNULAR EDGE HAVING BEEN COVERED WITH A LAYER OF SAID SUBSTANCE IN A SOLID STATE, WHICH HEALS ITSELF FROM THE LIQUID SUBSTANCE WHENEVER A BREAK OCURS, COOLING SAID EDGE TO KEEP SAID LAYER IN A SOLID STATE, AND ADJUSTING THE ANGULAR VELOXITY OF THE ROTOR TO POUR A CONTINUOUS SHEET OF SAID SUBSTANCE IN A LIQUID STATE OVER SAID EDGE OF SAID ROTOR TO ALLOW SURFACE TENSION IN SAID SHEET TO CONTINUOUSLY FORM SAID SHEET INTO A MULTIPLICITY OF LIQUID FILAMENTS AND TO ALLOW THE KINETIC ENERGY OF THE MOLECULES OF SAID SUBSTANCE TO ATTENUATE SAID LIQUID FILAMENTS TO A DESIRED DIAMETER.
 4. THE COMBINATION OF A HOLLOW ROTOR HAVING AN INTERNAL WALL, MEANS FOR HEATING AN INORGANIC NON-GLASSFORMER SUBSTANCE TO A TEMPERATURE IN EXCESS OF 2000*C. TO RAPIDLY LIQUEFY SAID SUBSTANCE IN SAID ROTOR, MEANS FOR DEPOSIGINT SAID SUBSTANCE ON THE INTERNAL WALL, MEANS FOR ROTATING SAID ROTOR AT HIGH ROTATIONAL VELOCITIES, AND APERTURE MEANS IN SAID ROTOR FOR RELEASING A CONSTINUOUS SHEET OF SAID LIQUID SUBSTANCES FROM SAID ROTOR WHEREBY A MULTIPLICITY OF LIQUID FILAMENTS ARE FORMED BY SURFACE TENSION FROM SAID SHEET. 